Ravenfield map terrain limited size?

So I'm building a map for a game called Ravenfield using Unity and I've come to a point where I cannot expand the island any further. I think this is because there is no terrain left to pull up. Anyone have an idea of how to expand the area?

Sry my fault, you don't need to copy it, because then it's only a clone.
Here's the right guide:
-click on "Assets" (the folder below to the left)
-tipe in "Terrain"
-drag "ExampleSence Terrain and swipe it in your window

It would be in your main terrain, so u need to click on the terrian (which is in the console at least)
and choose move to move it.

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